No. 2.] THE ADHESIVE ORGAN OF AMIA. 475 
sac which separates the entoblast beneath the pericardial 
cavity from the yolk. The broad, flat, anterior end of the 
foregut extends forward to the stomodaeum where its greatly 
thickened anterior wall is-in contact with the ectoblast. 
From the dorsal wall of the short foregut rise three diver- 
ticula. The central one (Fig. C, med. div.) is thick-walled, 
with a very shallow cavity and forms the button. The lateral 
f, br. 
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is 
Fic. C—Median longitudinal section of an embryo of the stage shown 
in Plate, Fig. 2. Camera outline, details from photograph, * about 
150. med. diy., median diverticulum which produces the “button” 
seen in front of the forebrain between the paired diverticula in 
Plate, Fig. 2. Other letters as in Figs. A and B. The hypophysis, 
hy., is not accurately represented. 
diverticula are also thick-walled, but have long and narrow 
cavities. They leave the foregut at a point some distance from 
the middle line, ventral and anterior to the tip of the fore- 
brain, and pass upward, backward and outward, so that their 
free ends touch the sides of the forebrain immediately in 
front of the optic vesicles (Fig. B). These paired diverticula 
produce the rounded protuberances referred to above as the 
fundaments of the adhesive organ. The button and the ad- 
hesive organ have evidently been formed from the crescent 
of the preceding stage. The button may be considered as a 
remnant of the central portion of the original crescent. 
